Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1997-03-05
1999-03-23
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562599, C07C 5704, C07C 5702
Patent
active
058862200
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for preventing the polymerization of a vinyl compound. More particularly, it pertains to a process for preventing the polymerization of a vinyl compound which process is capable of effectively inhibiting the polymerization of acrylic acid, methacrylic acid or the like in the distillation system, etc. of the production process for the above-mentioned acid, etc. as well as the corrosion of the equipment and machinery to be used therein and at the same time, enables long-term stable continuous operation of the equipment and machinery.
BACKGROUND ART
It has heretofore been known that a vinyl compound such as styrene, acrylic acid, methacrylic acid, an acrylic ester, a methacrylic ester and acrylonitrile has the property of liability to polymerization by light, heat or the like. In the production process of the above-mentioned vinyl compound, various distillation operations are put into practice for the purpose of separating, recovering, concentrating or purifying the objective vinyl compound. However, the aforesaid vinyl compound is apt to bring about an unfavorable situation such as various troubles in the distillation step which finally make it impossible to proceed with a long-term stable continuous operation, since as mentioned above, the compound is liable to polymerization by light, heat or the like to form a polymer-like substance.
In order to avoid such a situation, there has heretofore been adopted a process in which the distillation operations are put into practice in the presence of a polymerization inhibitor, which is exemplified by hydroquinone, methoquinone (p-methoxyphenol), p-tert-butyl catechol, tert-butylhydroquinone and phenothiazine. Nevertheless, the actual situation is that any of the above-mentioned polymerization inhibitors does not necessarily exert sufficient effect on acrylic acid, methacrylic acid and the like because of their extreme liability to polymerization.
Aside from the foregoing, it is known that cupric dibutyldithiocarbamate is a substance which is capable of extremely effectively preventing the polymerization in liquid phase of acrylic acid, methacrylic acid, etc., but it has been difficult to employ the substance in an industrial manufacturing plant because of its fatal disadvantage that it corrodes an equipment made of, for example, SUS 316.
On the other hand, there is proposed a method in which a manganate is employed as a corrosion inhibitor in combination with a metallic salt of dithiocarbamic acid. (Refer to Japanese Patent Application Laid-Open No. 51403/1993). However, the aforesaid method is not satisfactory because of its insufficient corrosion inhibition effect.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide, under such circumstances, a process for preventing the polymerization of a vinyl compound which process is capable of efficiently inhibiting the polymerization of a vinyl compound, especially acrylic acid, methacrylic acid or the like in the distillation system, etc. of the production process for the above-mentioned acid, as well as the corrosion of the equipment and machinery to be used therein, and at the same time, enables long-term stable continuous operation of the equipment and machinery.
As a result of intensive research and investigation accumulated by the present inventors in order to attain the above-mentioned object, it has been found that the object can be attained by paying attention to the excellent corrosion inhibition effect of a metallic salt of dithiocarbamic acid typified by cupric dibutyldithiocarbamate and making use thereof in combination with a specific corrosion inhibitive substance typified by water. The present invention has been accomplished by the foregoing finding and information.
Specifically, the present invention provides a process for preventing the polymerization of a vinyl compound which comprises allowing water in an amount of 0.05 to 5% by weight based on the vinyl compound to coexist with a metallic salt of dithiocarbamic
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Lewis, Hawley's Condensed Chemical Dictionary, 12th edition, p. 908, 1993.
Mimaki Hideaki
Nakagawa Takashi
Okamoto Kenji
Tomita Kouji
Geist Gary
Idemitsu Petrochemical Co. Ltd.
Keys Rosalynd
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